On Mon, Dec 09, 2002 at 01:58:11PM -0800, Austin Hastings wrote:
> --- Adam Turoff <[EMAIL PROTECTED]> wrote:
> > I think you're trying to overoptimize something here. I can't see
> > a benefit to caching only sometimes. If there is, then you probably
> > want to implement a more sophisticated cache management strategy
> > for your sub, not warp the language for a special case.
>
> Ahh. This is better. How does one implement a more sophisticated cache
> management strategy?
By memoizing specific cases by hand, of course. :-)
> That is, what is the mechanism for manipulating the run-time system
> behavior of subs?
Memoization does not have to involve manipulating runtime behavior.
However, manipulating runtime behavior is a simple, generic and
effective way to memoize random subs.
Here's an example of a memoizing only the values for 'feb'.
Schwern's solution is simpler and easier to read though.
{
## start of a lexical scope to hide %feb_cache
my %feb_cache;
sub days_in_month(Str $month, Int $year) {
$month = lc $month;
if $month eq 'feb' {
unless $feb_cache{$year} {
my $leap = $year % 4 == 0
&& ($year % 100 != 0 || $year % 400 == 0);
$feb_cache{$year} = $leap ? 29 : 28;
}
return $feb_cache{$year};
} else {
return %days{$month};
}
}
}
Z.
